DANVILLE, Ky. — Vice President Joe Biden and challenger Paul Ryan were feisty and combative on Thursday night in their first and only debate, providing a relentless, quick-moving exchange that outlined stark differences between their campaigns.

From foreign policy to federal spending to health care, Biden and Ryan used statistics, rhetorical jabs, and humor to fashion a pointed discussion that differed strikingly from the debate last week in which President Obama often seemed listless and disengaged.

The candidates challenged each other when they disagreed on the facts, delivered their arguments with confidence, and brought a mutual passion to the debate at Centre College.

The debate opened with US foreign policy — in Iran, North Africa, and the Middle East — and on whether the deaths of four Americans in Libya one month ago had been the result of a massive intelligence failure. “We did not know they wanted more security there,” Biden said.

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Biden defended the Obama administration’s use of sanctions, which he says is crippling Iran, and warned Mitt Romney’s approach might lead to war instead. “The president of the United States has led with a steady hand and clear vision.” Biden said. Governor Romney, the opposite. The last thing we need now is another war.”

Ryan countered that Obama’s reluctance to be tougher on Iran is a critical mistake. “The ayatollahs see these kinds of statements and they think, ‘I’m going to get a nuclear weapon,’ ” the Republican congressman said.

The early focus on foreign policy seemed to play to Biden’s strengths. On Syria, the former Foreign Relations Committee chairman pushed back against Ryan’s argument that Obama was not quick enough to side with rebels there and condemn President Bashar Assad.

On Afghanistan, Biden staunchly defended the administration’s decision to pull out US troops by 2014. In the interim, Ryan said, the remaining troops have been put at risk by the ongoing withdrawal.

“No one got pulled out who didn’t get replaced by trained Afghan personnel,” Biden said.

When the debate turned to the economy, Biden ripped Romney for his comment about 47 percent of Americans not paying taxes, considering themselves “victims.”

“These people are my mom and dad — the people I grew up with, my neighbors,” Biden said. “They pay more effective tax than Governor Romney pays in his federal income tax.”

Ryan defended Romney, and talked about the Nixon family from Northborough, Mass., whom Romney helped after their sons were in a car accident. He noted Romney gave 30 percent of his income to charity, more than Ryan and Biden combined. And he argued the “47 percent” comment was a slip of the tongue and did not reflect how Romney really felt.

“I think the vice president very well knows that sometimes the words don’t come out of your mouth the right way,” Ryan said.

“But I always say what I mean,” Biden rebutted with a smile. “And so does Romney.”

“I don’t doubt his personal commitment to individuals,” Biden said of Romney, adding, “Stop talking about how you care about people. Show me something. Show me a policy where you take responsibility.”

Biden referred to Ryan as “my friend” numerous times, a rhetorical tool frequently used in the Senate where he served for 36 years.

Just several minutes into the debate, Biden delivered a line with the forcefulness many Democrats wished Obama had against Romney. “With all due respect, that’s a bunch of malarkey,” Biden said. “Not a single thing he said was accurate.”

Biden’s aggressive demeanor, often accompanied by a smirk and a willingness to talk over Ryan, seemed to answer the calls of many Democrats who had wished to see Obama challenge Romney that way.

The moderator, Martha Raddatz of ABC News, was more forceful than Jim Lehrer of PBS had been in Denver and worked to keep the candidates on point and within time limits.

Ryan criticized the Obama administration for the federal stimulus program, which Democrats cite as a reason the economy has improved, but Republicans have said is a boondoggle and waste of federal tax dollars.

“I love my friend here!” Biden said about Ryan. “He sent me two letters saying, by the way, ‘Can you send some stimulus money for companies here in the state of Wisconsin?’ ”

Biden referred to Ryan as “my friend” 14 times in the 90-minute debate.

Ryan conceded he had asked for federal stimulus funding for projects in his district, but said it was for constituent services.

But the Obama administration has failed to get the unemployment rate below 6 percent, as it suggested it could do with stimulus money, Ryan said.

“I don’t know how long it will take,” Biden responded, to get the unemployment rate down to 6 percent. “We can and we will get it under 6 percent.”

On the question of abortion, Ryan and Biden lowered their voices and spoke of how their Catholic faith affected their differing positions. Ryan said a Romney administration would oppose abortion except in the cases of rape, incest, or the life of the mother. Biden said he personally opposes abortion but does not believe he should impose those beliefs on others.

“I don’t see how a public person can separate their public life from their faith,” Ryan said. “I believe that life begins at conception, and that is why I am prolife.”

Biden warned a Romney administration might result in Supreme Court appointments that would outlaw abortion.

Both candidates entered the debate under rising pressure in the final weeks of a close, hard-fought campaign. Biden, however, seemed to shoulder more of a burden in the aftermath of Obama’s passive performance last week in the first presidential debate in Denver.

Although vice presidential debates rarely affect the top of the ticket, Democrats hoped Biden’s hard-hitting style would counter Ryan effectively and calm rising party anxiety. Since the Denver debate, some polls have showed Romney inching past Obama, whose once-growing lead has shriveled in many battleground states.

In that single debate last week, Romney dramatically reset the dynamic of the campaign, which had been shifting slowly in Obama’s favor.

On Thursday night, Obama told reporters he thought Biden was “terrific” in the debate and said he called him afterward. “I could not be prouder of him,” Obama said. “I thought he made a very strong case.”

Romney’s campaign said he called Ryan about 10 minutes after the debate, congratulating him on a “fantastic” showing, adding that his family should be proud.

Republicans were hopeful that Ryan’s down-to-earth demeanor and youthful confidence would appeal to millions of voters who heard him Thursday for the first time, as he tried to sell the deep budget cuts that he and Romney are proposing as a path toward fiscal stability. A seven-term Wisconsin congressman, Ryan prepared for the debate — his first on the national stage — with the kind of demanding repetition that he brings to his exhausting physical workouts, Republican aides said. Former solicitor general Ted Olson, who served under President George W. Bush, played Biden in the rehearsals.

As chairman of the House Budget Committee, Ryan brought deep, broad knowledge of federal spending to the debate. He also brought controversy with his proposal, endorsed by Romney, that Medicare be overhauled by offering recipients a limited cash voucher to buy private insurance.

Obama and Biden have attacked that idea as dismantling the longstanding health care compact between the elderly and government.

Such vouchers, they say, would not keep pace with rising medical costs and would impose additional financial burden on people with limited, fixed incomes.

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